Conversion of alcohols or ethers using rare earth crystalline aluminosilicate in an alumina matrix

ABSTRACT

An improved process using a rare earth-containing catalyst is provided. The catalyst comprises a composite of matrix and rare earth or of zeolite, rare earth and matrix, usually alumina. The rare earth can be a single metal or a mixture of rare earth metals. The process involved is the conversion of alcohols or ethers to gasoline boiling range hydrocarbons.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a division of copending application Ser. No. 794,163filed May 5, 1977, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a process of converting alcohols or ethers togasoline fractions by passing them over a catalyst comprising acomposite of a zeolite, and/or a matrix material and a rare earth metalor mixtures of such metals.

2. Description of the Prior Art

A continuing growth in the production of synthetic fibers, plastic andrubber has taken place in recent decades. This growth, to a very largeextent, has been supported and encouraged by an expanding supply ofpetrochemical raw materials such as ethylene, benzene, toluene, andxylenes. Side by side with this development, there has been anincreasing demand for aromatic hydrocarbons for use as high octanegasoline components. Environmental factors which limit the lead contentof gasoline are likely to aggravate the need for aromatics.

Burgeoning demand for olefins, particularly ethylene, and for aromatichydrocarbons, has of course led to periods of shortage, either due toshort supply of suitable feedstocks or to limited processing capacity.In any case, it would appear desirable to provide efficient means forconverting raw materials other than petroleum to olefins and aromatichydrocarbons.

The process described herein employs zeolites that are known in the art.ZSM-5, for example, is disclosed and claimed in U.S. Pat. No. 3,702,886.A description of ZSM-11 may be found in U.S. Pat. No. 3,709,979 andZSM-12 in West German Offenlaugunschrifft No. 2,213,109. The patentsreferred to are incorporated herein by reference.

ZSM-4 is described in U.S. Pat. No. 3,923,639, and the descriptivematter of this patent relating to such zeolite is hereby incorporated byreference in this application.

ZSM-35 is disclosed in U.S. application Ser. No. 528,061, filed Nov. 29,1974. Descriptions of ZSM-38 and ZK-4 can be found in U.S. applicationSer. No. 560,412, filed Mar. 20, 1975 and U.S. Pat. No. 3,140,252,respectively. So these zeolites may be completely described, theseapplications and the patent are incorporated herein by reference.

U.S. Pat. No. 3,816,342 claims a process involving exchanging a zeolite,calcining it, compositing it with a matrix and exchanging it again. Thecatalyst is disclosed as being useful in hydrocarbon conversionreactions.

SUMMARY OF THE INVENTION

In accordance with the present invention, there are provided a processfor converting a feed comprising a C₁ -C₄ monohydric alcohol to itsether using a rare earth alumina catalyst and a process for convertingsaid alcohol, its ether derivative or mixtures thereof to a gasolineboiling range hydrocarbon or to a light olefin such as C₂ ═ bycontacting the latter feed with a composite comprising a zeolite, amatrix therefor and a rare earth metal mixture of rare earth metals. Thecatalyst per se is also provided by the invention.

DESCRIPTION OF SPECIFIC EMBODIMENTS

Any composition consisting essentially of one or more monohydricalcohols having from 1 to 4 carbon atoms, mixtures thereof and mixtureswith the compounding ethers, may be used as feed to the process of thisinvention. Thus, methanol, ethanol, n-propanol, isopropanol, n-butanol,sec-butanol and isobutanol may be used either alone or in admixture withone another. The ethers useful in the invention include, alone, or inadmixtures, dimethyl, diethyl, dipropyl and dibutyl ethers, as well asmethylethyl ether and the like. Particularly preferred feeds aremethanol, dimethyl ether and mixtures thereof.

The zeolites that may be used include the natural zeolites such asmordenite, erionite, chabazite, clinoptilolite, offretite, mazzite andthe like as well as the synthetic zeolites Alpha, Beta, ZSM-4, ZSM-5,ZSM-11, ZSM-12, ZSM-35 and ZSM-38.

The alumina matrix or carrier useful in the invention may be any aluminathat has a high surface area (i.e. >50m² /g) and exhibits good bindingproperties. Aluminas meeting these criteria are the gamma, eta, chi,rho, or kappa forms thereof. There matrix materials may be formed usingthe appropriate hydrated alumina forms, such as the pseudoamorphoustrihydrate, β-trihydrate, α-monohydrate, pseudobohemite, γ-trihydrateand α-trihydrate and calcining the product.

Rare earth elements that may be used alone or in combination includelanthanum, cerium, praseodymium, neodymium,, promethium, samarium,europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium,ytterbium, ytterium and lutetium. The rare earth element, expressed interms of its oxide, RE₂ O₃, is employed within the range of from about1% to about 30% by weight of the matrix, preferably from about 2% toabout 20%. This means that, of the RE₂ O₃.Al₂ O₃ portion, the Al₂ O₃content will range from about 99% to about 70% by weight of the total.

With respect to the composite, it will comprise from about 5% to about80% by weight thereof of the zeolite, preferably from about 20% to about75%, and from about 95% to about 20% by weight of RE₂ O₃.Al₂ O₃,preferably from about 80% to about 25%.

The rare earth elements may be incorporated with the alumina as salts orhydrated oxides. The alumina itself may be impregnated with the REsalts, as, for example, nitrate or halide. The RE₂ O₃.Al₂ O₃ portion isthen mixed with the zeolite in any way suitable, the composite is formedinto suitable sizes and shapes and is calcined at a temperature of fromabout 800° F. to about 1700° F. For maximum inertness of the matrix, thecalcination is carried out within the range of from about 1200° F. toabout 1700° F., but below the temperature at which substantial zeolitedestruction occurs.

In preparing the composite, the zeolite and alumina (which may containabout 1-10% by weight of SiO₂ as a stabilizing agent) may be mixedbefore the rare earth element is added. In this case, the rare earth canbe added by impregnation and then treated as outlined already.

The zeolites, whether per se or in the composite, or whether having rareearth elements incorporated therewith or not, are capable of having atleast a portion of the original cations associated therewith replaced bya wide variety of other cations according to techniques well known inthe art. Replacing cations include ammonium and metal cations, includingmixtures of the same. The zeolite employed as catalyst in this inventionmay be prepared from zeolites wherein at least a portion of the originalcations associated therewith have been replaced by hydrogen.

The crystalline aluminosilicate zeolites can be converted to thehydrogen form, i.e., having at least a portion of the original cationsassociated therewith replaced by hydrogen, generally by two methods. Thefirst involves direct ion exchange employing an acid. Suitable acidsinclude both inorganic acids and organic acids. Typical inorganic acidswhich can be employed include hydrochloric acid, hydrosulfuric acid,nitric acid, nitrous acid, hyponitrous acid, phosphoric acid, andcarbonic acid. Typical organic acids which can be employed are themonocarboxylic and polycarboxylic acids which can be aliphatic,aromatic, or cycloaliphatic in nature. Representative suitable acidsinclude acetic, trichloroacetic, bromoacetic, citric, maleic, fumaric,itaconic, phenylacetic, benzene sulfonic and methane sulfonic acids. Thesecond method for preparing the hydrogen form, which is preferred,involves first preparing an ammonium or other hydrogen ion precursorform by base exchange and then calcining to cause evolution of theammonia leaving a hydrogen ion remaining on the zeolite. Calcining iscarried out in air at 400° C.-600° C. for about 15 minutes to about 24hours. Suitable compounds for preparing the hydrogen ion precursor forminclude ammonium compounds such as the chloride, bromide, iodide,bicarbonate, sulfate, citrate, borate, and palmitate. Still otherammonium compounds which can be employed include quaternary ammoniumcompounds such as tetramethylammonium hydroxide and trimethylammoniumchloride.

In the process of this invention, the feed consisting essentially of oneor more of the lower alcohols or ethers derived therefrom is contactedwith the above-described catalyst at a temperature of about 250° C. toabout 700° C., and preferably about 350° C. to 500° C.; a contact timeequivalent to or the same as a weight hourly space velocity (WHSV) ofabout 0.5 to 50, preferably about 1.0 to 10.0, it being understood thatWHSV signifies pounds of feed per pound of catalyst per hour; and at anabsolute pressure of about 0.2 to 30 atmospheres. The catalyst may be inthe form of fixed bed, fixed fluid bed, or it may be of the transportbed type.

The product stream in the process of this invention contains steam and ahydrocarbon mixture comprising light olefins and aromatic hydrocarbons.

The predominant aromatic hydrocarbons are monocyclic hydrocarbons suchas benzene, toluene and xylene. Thus, they are all valuablepetrochemicals. The steam and hydrocarbons are separated from oneanother by methods well known in the art. The proportions may be variedby selecting reaction conditions within the purview specified above,olefins being favored by lower temperatures and in general by lesssevere conversion conditions.

Catalyst deactivated by coke deposited during the process may bereactivated by controlled regeneration using an oxygen containingregeneration medium and controlling the operating conditions to limitthe maximum catalyst temperature to about 600° C. Such a regenerationcan be completed in less than about 24 hours. Operation of the processof this invention in the presence of added hydrogen may sometimes retardaging.

It is not fully understood why the composite catalyst of this inventionproduces such desirable products. Nonetheless, the conversion of asingle carbon feed, such as methanol, or its ether, with such highselectivity to monocyclic aromatics, is surprising.

Having described the invention in general terms, the following Examplesare offered as illustrations. It is to be understood that they aremerely illustrative and are not intended to limit the invention.

EXAMPLE 1

Alpha-alumina monohydrate was formed into extrudates, dried and calcinedat 1400° F. in air. The calcined alumina extrudate was impregnated withan aqueous solution containing 17.3% of mixed rare earth chlorides to alevel of 2.6 wt. % RE₂ O₃, then recalcined at 1000° F. Rare earthsolutions typically have the following composition:

    ______________________________________                                        Ce as CeO.sub.2                                                                              =       48% by weight                                          La as La.sub.2 O.sub.3                                                                       =       24% by weight                                          Pr as Pr.sub.6 O.sub.11                                                                      =        5% by weight                                          Nd as Nd.sub.2 O.sub.3                                                                       =       17% by weight                                          Sm as Sm.sub.2 O.sub.3                                                                       =        3% by weight                                          Gd as Gd.sub.2 O.sub.3                                                                       =        2% by weight                                          Other rare                                                                    earth oxides   =        0.8% by weight                                        ______________________________________                                    

To determine the effectiveness of the rare earth deactivation, thematerial was evaluated for the conversion of methanol to dimethyl etherat 850° F., since at this temperature alumina is a known catalyst forthe decomposition of methanol into CO and H₂. The results are presentedin Table 1 and are compared to those obtained with the same aluminastarting material that had been calcined at 1200° F. without theaddition of rare earth. These data show 15.1% by weight of CO in theproduct for the alumina alone while the rare earth-alumina gave only1.5% by weight CO in the product.

                  TABLE 1                                                         ______________________________________                                        METHANOL DEHYDRATION                                                                   Catalyst Description                                                                     Kaiser Al.sub.2 O.sub.3 calcined                                   Kaiser     at 1400° F., impregnated                                    Al.sub.2 O.sub.3 calcined                                                                with RECl.sub.3 to 2.6%                                            at 1200° F.                                                                       wt RE.sub.2 O.sub.3                                       ______________________________________                                         Operating                                                                    Conditions                                                                     Feed Comp.                                                                              100% MeOH     84% MeOH                                                                      16% H.sub.2 O                                         Pressure, psig                                                                          235          235                                                    WHSV, Hr   9.8          9.5                                                   Temp., Avg. ° F.                                                                 852          854                                                    Temp., Max. ° F.                                                                 861          875                                                    MeOH Conv.,                                                                              83.6         74.9                                                 % Wt.                                                                         Product Analysis,                                                             % by Weight                                                                    H.sub.2 O  21.2         24.5      21.7.sup.1                                  MeOH       16.6         21.5      25.7                                        DME        40.2         41.5      49.6                                        CO         15.1         1.5        1.8                                       ______________________________________                                         .sup.1 Calculated assuming 100% MeOH feed.                               

EXAMPLE 2

A catalyst comprising 65% ZSM-5 and 35% Al₂ O₃ was processed into thecatalytic acid form (i.e., exchange with the NH₄ ⁺, followed bycalcination). The catalyst was impregnated with an aqueous solutioncontaining 4.2% by weight of mixed RE(NO₃)₃ to give a finished contentof 1.1% RE₂ O₃ on the overall catalyst. It was then dried and calcinedat 1000° F. The catalyst was evaluated for the conversion of methanol togasoline boiling range hydrocarbons. The results presented in Table 2show the rare earth treated catalyst to give lower CO content, amethanol decomposition product, in the product at temperatures greaterthan 350° F. The data also indicate a higher aromatic content of thehydrocarbon product when using the rare earth treated catalyst. The rareearth in RE(NO₃)₃ was essentially the same as outlined in Example 1.

    ______________________________________                                        METHANOL CONVERSION TO GASOLINE                                                           Catalyst Description                                                                    65% ZSM-5, 35% Al.sub.2 O.sub.3                                     65% ZSM-5 Impregnated to                                                      35% Al.sub.2 O.sub.3                                                                    3.3% RE.sub.2 O.sub.3                                   ______________________________________                                        Operating Conditions                                                           Pressure, psig                                                                             150         150      150                                         WHSV, hr.    5.7         5.7      5.7                                         Temp., Avg., ° F.                                                                   861         855      864                                         Temp., Max., ° F.                                                                   883         878      895                                        Product Analysis                                                               C.sub.5 +, % by weight                                                                     48.3        51.9     60.3                                        Aromatics, % 18.4        23.2     25.4                                        by weight                                                                     CO, % by weight                                                                            1.1         0.8      0.6                                        ______________________________________                                    

1. A process for converting a feed comprising a C₁ -C₄ monohydricalcohol, its ether derivative or mixtures thereof to a gasoline boilingrange hydrocarbon by contacting said feed with a composite consistingessentially of a rare earth alumina matrix and a crystalline
 2. Theprocess of claim 1 wherein rare earth, expressed in terms of RE₂ O.sub.3, is present in an amount of from about 1% to about 30%
 4. The processof claim 1 wherein in said composite the rare earth alumina matrix israre earth-alumina expressed as RE₂ O₃ --Al₂ O₃ and wherein such ispresent in the composite to the extent of from
 5. The process of claim 4wherein the zeolite is present in the composite
 6. The process of claim5 wherein the rare earth is selected from the group consisting oflanthanum, cerium, praseodymium, neodymium, promethium, samarium,europium, gadolinium, terbium, dysprosium, halmium, erbium,
 7. Theprocess of claim 1 wherein the rare earth is combined with the
 8. Theprocess of claim 1 wherein the zeolite and matrix are composited
 9. Theprocess of claim 1 wherein the zeolite is ZSM-5, the matrix is aluminaand the rare earth is from mixed rare earths.